Abstract: Modern firm theory brought about profound effects on the construction of modern corporate law theory and system. This article focuses on the internal relationship of modern firm theory, corporate law theory and corporate system by summarizing the idea of non-complete contract theory and property right theory of modern firm theory, and exploring the response of corporate law and system to modern firm theory. It shows non-complete contract theory directly leads to the formation of corporate contract theory, which is embodied in a large number of default and enabling rules and emphasis on market mechanism centered on information disclosure in terms of corporate system. And the agency theory, stakeholder theory and system construction are also influenced by modern firm theory.